Performance of a BP c-Si building Integrated PV system after 15years of installation

In this study, the performance, yield and characteristics of a 15 year old photovoltaic system installation has been investigated. The technology, BP Saturn modules which were steel-blue polycrystalline silicon cells are no longer in production. A bespoke monitoring system was designed and purpose built to monitor the characteristics of 6 strings, of 18 modules connected in series. The total output of the system is configured to 6.5kWp (series to parallel configuration). The PV system is demonstrating system outputs to be inferior by 0.7% per year. However,efficiency values in comparison to standard test conditions have remained practically the same. This output though very relevant to the possible performance and stability of aging cells, requires additional parametric studies to develop a more robust argument. The result presented in this paper is part of an on going investigation into PV system aging effects.

Assessing the performance of a building integrated BP c-Si PV system

In this study, the performance, yield and characteristics of a 16 year old photovoltaic (PV) system installation have been investigated. The technology, BP Saturn modules which were steel-blue polycrystalline silicon cells are no longer in production. A bespoke monitoring system has been designed to monitor the characteristics of 6 refurbished strings, of 18 modules connected in series. The total output of the system is configured to 6.5 kWp (series to parallel configuration). In addition to experimental results, the performance ratio (PR) of known values was simulated using PVSyst, a simulation software package. From calculations using experimental values, the PV system showed approximately 10% inferior power outputs to what would have been expected as standard test conditions. However, efficiency values in comparison to standard test conditions and the performance ratio (w75% from PVSyst simulations) over the past decade have remained practically the same. This output though very relevant to the possible performance and stability of aging cells, requires additional parametric studies to develop a more robust argument. The result presented in this paper is part of an on-going investigation into PV system aging effects.

An interpretation of baroclinic initial value problems: results for simple basic states with nonzero interior PV gradients

In the Eady model, where the meridional potential vorticity (PV) gradient is zero, perturbation energy growth can be partitioned cleanly into three mechanisms: (i) shear instability, (ii) resonance, and (iii) the Orr mechanism. Shear instability involves two-way interaction between Rossby edge waves on the ground and lid, resonance occurs as interior PV anomalies excite the edge waves, and the Orr mechanism involves only interior PV anomalies. These mechanisms have distinct implications for the structural and temporal linear evolution of perturbations. Here, a new framework is developed in which the same mechanisms can be distinguished for growth on basic states with nonzero interior PV gradients. It is further shown that the evolution from quite general initial conditions can be accurately described (peak error in perturbation total energy typically less than 10%) by a reduced system that involves only three Rossby wave components. Two of these are counterpropagating Rossby waves—that is, generalizations of the Rossby edge waves when the interior PV gradient is nonzero—whereas the other component depends on the structure of the initial condition and its PV is advected passively with the shear flow. In the cases considered, the three-component model outperforms approximate solutions based on truncating a modal or singular vector basis.

The impact of moist processes on the African easterly jet-African easterly wave system

The African Easterly Jet-Easterly Wave (AEJ-AEW) system was explored in an idealised model. Prescribed zonally symmetric surface temperature and moisture profiles determine the AEJ which becomes established through meridional contrasts in dry and moist convection.As in previous studies, a realistic AEJ developed with only dry convection. Including moist processes, increased its development rate, but reduced its speed and meridional extent. AEWs grew through barotropic-baroclinic conversions. Negative meridional potential vorticity (PV) gradients arose in the zonally symmetric state through the intrusion of the low-PV Saharan boundary layer. Since moist processes strengthened this significantly through diabatically generated PV in the Intertropical Convergence Zone, moist AEWs were three times stronger. Larger barotropic conversions and faster AEJ development increased the moist wave growth-rate. Jet-level and northerly low-level amplitudes grew, but in the moist case the low-level amplitudes weakened as the AEW interacted with convection, consistent with their absence from observations during the peak monsoon. Striking dependencies between the AEJ, AEW and rainfall existed. Two time-scales governed their evolution, depending on the transfer coefficients: (1) the AEJ's replenishment rate influenced by heat fluxes, and (2) the wave growth-rate, by damping, and the slower jet development rate.Moist AEWs were characterized by intermittent growth/decay, with growth preceded by increased mean rainfall and later, weakening AEJs. These dependencies established an internal 8-10-day variability, consistent with intra-seasonal observations of 9-day rainy sequences. This internal variability offers an alternative explanation to the previously proposed external forcing and a new view of the moist AEW life cycle. Copyright © 2009 Royal Meteorological Society

How well does the ECMWF Ensemble Prediction System predict blocking?

Forecasting atmospheric blocking is one of the main problems facing medium-range weather forecasters in the extratropics. The European Centre for Medium-Range Weather Forecasts (ECMWF) Ensemble Prediction System (EPS) provides an excellent basis for medium-range forecasting as it provides a number of different possible realizations of the meteorological future. This ensemble of forecasts attempts to account for uncertainties in both the initial conditions and the model formulation. Since 18 July 2000, routine output from the EPS has included the field of potential temperature on the potential vorticity (PV) D 2 PV units (PVU) surface, the dynamical tropopause. This has enabled the objective identification of blocking using an index based on the reversal of the meridional potential-temperature gradient. A year of EPS probability forecasts of Euro-Atlantic and Pacific blocking have been produced and are assessed in this paper, concentrating on the Euro-Atlantic sector. Standard verification techniques such as Brier scores, Relative Operating Characteristic (ROC) curves and reliability diagrams are used. It is shown that Euro-Atlantic sector-blocking forecasts are skilful relative to climatology out to 10 days, and are more skilful than the deterministic control forecast at all lead times. The EPS is also more skilful than a probabilistic version of this deterministic forecast, though the difference is smaller. In addition, it is shown that the onset of a sector-blocking episode is less well predicted than its decay. As the lead time increases, the probability forecasts tend towards a model climatology with slightly less blocking than is seen in the real atmosphere. This small under-forecasting bias in the blocking forecasts is possibly related to a westerly bias in the ECMWF model. Copyright © 2003 Royal Meteorological Society

Hcp2, a secreted protein of the phytopathogen Pseudomonas syringae pv. tomato DC3000, is required for competitive fitness against bacteria and yeasts

When analysing the secretome of the plant pathogen Pseudomonas syringae pv. tomato (Pst) DC3000, we identified hemolysin co-regulated protein (Hcp) as one of the secreted proteins. Hcp is assumed to be an extracellular component of the type VI secretion system (T6SS). Two copies of hcp genes are present in the Pst DC3000 genome, hcp1 (PSPTO_2539) and hcp2 (PSPTO_5435). We studied the expression patterns of hcp genes and tested the fitness of hcp knock-out mutants in host plant colonization and in inter-microbial competition. We found that the hcp2 gene is expressed, most actively at the stationary growth phase, and that the Hcp2 protein is secreted via T6SS and appears in the culture medium as covalently linked dimers. Expression of hcp2 is not induced in planta and it does not contribute to virulence or colonisation in tomato or Arabidopsis plants. Instead, hcp2 is required for survival in competition with enterobacteria and yeasts, and its function is associated with suppression of the growth of these competitors. This is the first report on bacterial T6SS-associated genes functioning in competition against yeast. Our results suggest that the T6SS of P. syringae may play an important role in bacterial fitness, allowing this plant pathogen to survive in conditions where it has to compete with other micro-organisms for resources.

Simulations of a photovoltaic-thermal ground source heat pump system

A ground source heat pump assisted by an array of photovoltaic (PV)-thermal modules was studied in this work. Extracting heat from an array of PV modules should improve the performance of both the PV cells and the heat pump. A series of computer simulations compare the performance of a ground source heat pump with a short ground circuit, used to provide space heating and domestic hot water at a house in southern England. The results indicate that extracting heat from an array of PV-thermal modules would improve the performance of a ground source heat pump with an undersized ground loop. Nevertheless, open air thermal collectors could be more effective, especially during winter. In one model more electricity was saved in ohmic heating than was generated by cooling the PV cells. Cooling the PV modules was found to increase their electrical output up to 4%, but much of the extra electricity was consumed by the cooling pumps.